Imagine a thief stealing a little tiny bit of your vision every day, over the course of years, starting with your peripheral vision. Normally, we don’t pay much attention to our peripheral vision and we assume that how we are seeing is normal. A slow, progressive loss of peripheral vision sensitivity is the natural course of the most common type of glaucoma, primary open angle glaucoma, a disease affecting the optic nerve and it’s neurons. It is not until significant damage has occurred to the optic nerve and there is a profound loss of peripheral vision that a person will realize there might be a problem.
It is difficult to understand the value of our ability to perceive the world using our five senses until one of the senses is defective, as those who have lost vision or hearing will attest. Many types of vision loss can be restored using glasses, therapy, medicine or surgery. Vision loss from glaucoma cannot be reversed, only prevented in the first place. Glaucoma is the second leading cause of blindness in the world. It is one of the reasons eye care professionals recommend regular eye examinations.
The optic nerve contains about 1 million neurons that transmit visual information from the eye to the brain. As we age, we naturally lose a few neurons year by year. When this destruction of healthy neurons is accelerated in a specific manner, it is called glaucoma. There are several types of glaucoma but I will discuss just two, primary open angle glaucoma and acute angle closure glaucoma.
The causes of primary open angle glaucoma are not yet completely understood. We know there are several risk factors for glaucoma such as elevated eye pressure, age, family history, ethnicity (such as African-American), corneal thickness, general health conditions, previous eye disease and use of certain eye medications. Glaucoma is not diagnosed with just one test and it can present quite differently between individuals. Elevated eye pressure is not always present and some people will develop glaucoma in spite of low eye pressures. Often glaucoma is diagnosed by observing changes in the eye and eye function over time. During a routine eye examination your optometrist will use special instruments to examine the optic nerve’s structure at the back of the eye for signs of glaucoma. The optometrist will also inquire about risk factors, screen for peripheral vision problems and measure the eye’s pressure. If there are risk factors or suspicious findings, the optometrist will do follow-up testing that might include detailed peripheral vision testing, pachymetry (measuring the corneal thickness), gonioscopy (using a special lens to examine an internal eye structure called the trabecular meshwork) and optical coherence tomography (measuring the thickness of the neuron layer around the optic nerve). Sometimes initial testing neither confirms nor rules out glaucoma and testing needs to be repeated over months and sometimes years to be certain of the diagnosis.
Treatment for primary open angle glaucoma is recommended following diagnosis or with a high level of suspicion or risk of vision loss. The goal of treatment is to prevent further vision loss by lowering the eye pressure to a level where damage to the optic nerve would be minimized. Treatment can involve prescription eye drops, laser, surgery or a combination of these. Frequent follow-up is important to ensure the treatment is effective in halting damage to the optic nerve. Glaucoma is a chronic condition that requires monitoring, usually for the rest of one’s life.
Acute angle closure glaucoma is much less common and presents very differently. There is a fluid within the eye called aqueous humour that is constantly being produced and drained. The aqueous fluid pressure “inflates” the eye giving it a normal structure. The aqueous is continually drained through the trabecular meshwork which is located in an angle where the iris and the cornea meet near the front of the eye. If the iris is too close to the cornea, for one of a few possible reasons, the angle may close, blocking the trabecular meshwork “drain” and the eye pressure then builds up rapidly, sometimes within just a few hours. When this happens, it causes blurred vision and intense eye pain. This is an eye emergency and requires immediate attention by your optometrist, ophthalmologist or emergency department in order to preserve vision. Your optometrist can tell you if you are a higher risk for acute angle closure glaucoma during a routine eye examination.
Don’t allow the “silent thief” to steal one of your most precious senses. At Teeple Optometry, all the optometrists are trained to diagnose and treat glaucoma. Make sure to have regular eye examinations as recommended by your optometrist.